There is a growing demand for polymer materials that contain less impurities, particularly in the electronic and medical industries. While there are various methods for purifying certain kinds of polymer materials, there is still a need for an economical and versatile method to purify tacky and/or low cohesive strength polymer compositions. Tacky polymer compositions are often useful in pressure-sensitive adhesive compositions. Low-cohesive polymer compositions include extrudable materials that may be tacky or non-tacky.
Tacky, pressure sensitive adhesive (PSA) compositions are well known in the industry. Representative PSA polymers include (meth)acrylate copolymers, polyalphaolefin polymers, silanes, rubbers, block copolymers, and the like. Some PSA compositions have been described in U.S. Pat. Nos. 5,644,007; 4,751,087; 4,737,577; and Re. (Reissue) 24,906; all of which are incorporated herein by reference.
PSA polymers are made by polymerization reactions in which the reaction product may comprise residual monomer, low molecular weight (e.g. weight average molecular weight of 1000 or less) oligomeric by-products, catalyst, residual crosslinking promoters, and/or other impurities. In today's market, the specifications for PSA polymers are becoming more and more strict to the point where previously acceptable levels of such impurities are no longer tolerated.